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Date:      Fri, 30 Oct 1998 10:29:58 -0800
From:      Mike Smith <mike@smith.net.au>
To:        John Polstra <jdp@polstra.com>
Cc:        current@FreeBSD.ORG
Subject:   Re: New boot loader and alternate kernels 
Message-ID:  <199810301829.KAA01109@dingo.cdrom.com>
In-Reply-To: Your message of "Fri, 30 Oct 1998 10:17:11 PST." <199810301817.KAA12367@austin.polstra.com> 

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> I have a question about the new boot loader.  My /boot/boot.conf
> file looks like this:
> 
>     load /kernel
>     autoboot 10
> 
> Now suppose I want to boot an alternate kernel.  To do that, it seems
> I have to interrupt the autoboot sequence by pressing a key, then do
> "unload /kernel", then do "boot /kernel.alt".  Is that right?  It's
> the unload step that I'm wondering about.  Can it be avoided?

Unloading is an all or nothing proposition; it throws everything away 
(it doesn't take any arguments).  This avoids having holes in the 
loaded region, as well as having to deal with dependancy issues.

You can use the fact that 'boot' and 'autoboot' will look for a kernel 
for you to avoid having to load a kernel explicitly in your default 
case.

The variable $bootfile is a comma-separated list of kernel names to try 
to boot.  By default, it's implicitly set to 'kernel,kernel.old'.

In your current case, you could leave your /boot/boot.conf file empty, 
because the default behaviour is to wait 10 seconds and then boot.

If you wanted the equivalent of 

	load /kernel.test
	autoboot 10

but without needing to unload the kernel, you could say:

	set bootfile=/kernel.test
	autoboot 10

(Yes, the comma-separated list sucks.  I'm not sure what would be a 
 better approach; I had reasons for not using semicolons that I've now
 forgotten.)

-- 
\\  Sometimes you're ahead,       \\  Mike Smith
\\  sometimes you're behind.      \\  mike@smith.net.au
\\  The race is long, and in the  \\  msmith@freebsd.org
\\  end it's only with yourself.  \\  msmith@cdrom.com



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